The present invention relates to a white balance controller for an image pickup apparatus such as a video camera and, more particularly, to a white balance controller for performing a stabilized white balance controlling function under light sources whose color temperature changes.
Conventional apparatus of the described type, as disclosed in Japanese Laid-open Patent Publication No. 63-219291 corresponding to U.S. Pat. No. 4,797,733, enable white extraction treatment using a fixed threshold value to the amplitude of the color difference signals (or the signals used for calculating the color difference signals) after effecting white balance adjustment.
In the above described prior art, attention was only paid to the saturation of a colored portion in a state having white balance achieved, and no consideration was given to the condition of the color temperature of the lighting.
Further, in the above described prior art, not much attention was given to the automatic exposure control characteristic against the white ratio of the picture or the sensitivity of the image pickup element, and in view thereof the detection level sometimes became improper depending on the object of the viewing or the lighting.